JPH04335329A - Production of second harmonic generating element having dielectric polarization inversion grating - Google Patents
Production of second harmonic generating element having dielectric polarization inversion gratingInfo
- Publication number
- JPH04335329A JPH04335329A JP10606091A JP10606091A JPH04335329A JP H04335329 A JPH04335329 A JP H04335329A JP 10606091 A JP10606091 A JP 10606091A JP 10606091 A JP10606091 A JP 10606091A JP H04335329 A JPH04335329 A JP H04335329A
- Authority
- JP
- Japan
- Prior art keywords
- substrate
- temperature
- polarization inversion
- harmonic
- manufacturing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000010287 polarization Effects 0.000 title claims abstract description 91
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 23
- 239000000758 substrate Substances 0.000 claims abstract description 84
- 239000013078 crystal Substances 0.000 claims abstract description 33
- 238000000034 method Methods 0.000 claims abstract description 31
- 230000002269 spontaneous effect Effects 0.000 claims abstract description 29
- 239000010409 thin film Substances 0.000 claims abstract description 28
- 239000012535 impurity Substances 0.000 claims abstract description 20
- 150000002500 ions Chemical class 0.000 claims abstract description 20
- 229910001428 transition metal ion Inorganic materials 0.000 claims abstract description 7
- 239000000126 substance Substances 0.000 claims abstract 4
- 230000003287 optical effect Effects 0.000 claims description 43
- 238000010438 heat treatment Methods 0.000 claims description 28
- 238000002513 implantation Methods 0.000 claims description 13
- 239000002253 acid Substances 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 claims description 6
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 6
- AWJDQCINSGRBDJ-UHFFFAOYSA-N [Li].[Ta] Chemical compound [Li].[Ta] AWJDQCINSGRBDJ-UHFFFAOYSA-N 0.000 claims description 6
- 229910001413 alkali metal ion Inorganic materials 0.000 claims description 6
- 229910001882 dioxygen Inorganic materials 0.000 claims description 6
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 6
- 239000011777 magnesium Substances 0.000 claims description 6
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 5
- 229910052749 magnesium Inorganic materials 0.000 claims description 5
- 229910003002 lithium salt Inorganic materials 0.000 claims description 4
- 159000000002 lithium salts Chemical class 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 238000010494 dissociation reaction Methods 0.000 claims description 3
- 230000005593 dissociations Effects 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 3
- 238000005342 ion exchange Methods 0.000 claims description 2
- 229910003327 LiNbO3 Inorganic materials 0.000 claims 1
- 229910012463 LiTaO3 Inorganic materials 0.000 claims 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims 1
- 229910052744 lithium Inorganic materials 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 18
- 230000008569 process Effects 0.000 abstract description 8
- 229910021645 metal ion Inorganic materials 0.000 abstract 1
- 239000010936 titanium Substances 0.000 description 29
- 238000009792 diffusion process Methods 0.000 description 27
- 238000010586 diagram Methods 0.000 description 14
- 229920002120 photoresistant polymer Polymers 0.000 description 14
- 239000011295 pitch Substances 0.000 description 13
- 239000000463 material Substances 0.000 description 11
- 230000005684 electric field Effects 0.000 description 8
- 239000010408 film Substances 0.000 description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 5
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 4
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 description 4
- 230000008878 coupling Effects 0.000 description 4
- 238000010168 coupling process Methods 0.000 description 4
- 238000005859 coupling reaction Methods 0.000 description 4
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 description 4
- 238000005468 ion implantation Methods 0.000 description 4
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 4
- 239000000395 magnesium oxide Substances 0.000 description 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 4
- 238000000206 photolithography Methods 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 4
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 150000001340 alkali metals Chemical class 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 230000004907 flux Effects 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 239000011259 mixed solution Substances 0.000 description 3
- 235000012239 silicon dioxide Nutrition 0.000 description 3
- 229910052723 transition metal Inorganic materials 0.000 description 3
- 150000003624 transition metals Chemical class 0.000 description 3
- 239000005711 Benzoic acid Substances 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 230000004075 alteration Effects 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 235000010233 benzoic acid Nutrition 0.000 description 2
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 2
- 230000005466 cherenkov radiation Effects 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229940031993 lithium benzoate Drugs 0.000 description 2
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 2
- 229910052808 lithium carbonate Inorganic materials 0.000 description 2
- LDJNSLOKTFFLSL-UHFFFAOYSA-M lithium;benzoate Chemical compound [Li+].[O-]C(=O)C1=CC=CC=C1 LDJNSLOKTFFLSL-UHFFFAOYSA-M 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 description 2
- 239000011698 potassium fluoride Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- RIUWBIIVUYSTCN-UHFFFAOYSA-N trilithium borate Chemical compound [Li+].[Li+].[Li+].[O-]B([O-])[O-] RIUWBIIVUYSTCN-UHFFFAOYSA-N 0.000 description 2
- 206010021143 Hypoxia Diseases 0.000 description 1
- FUJCRWPEOMXPAD-UHFFFAOYSA-N Li2O Inorganic materials [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 230000005465 channeling Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- XUCJHNOBJLKZNU-UHFFFAOYSA-M dilithium;hydroxide Chemical compound [Li+].[Li+].[OH-] XUCJHNOBJLKZNU-UHFFFAOYSA-M 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004453 electron probe microanalysis Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Inorganic materials O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 description 1
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 235000003270 potassium fluoride Nutrition 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/355—Non-linear optics characterised by the materials used
- G02F1/3558—Poled materials, e.g. with periodic poling; Fabrication of domain inverted structures, e.g. for quasi-phase-matching [QPM]
Abstract
Description
【産業上の利用分野】本発明は、光ディスク装置、レ−
ザプリンタ、その他の光応用装置の光源の短波長化に係
り、とくに波長が約８００ｎｍの半導体レ−ザ光を波長
が約４００ｎｍの青色光に変換するような、導波路型の
第２高調波発生素子（ＳＨＧ，Ｓｅｃｏｎｎｄ Ｈａｒ
ｍｏｎｉｃ Ｇｅｎｅｒａｔｏｒ）の製造方法に関する
。[Industrial Field of Application] The present invention relates to optical disc devices,
This is related to the shortening of the wavelength of light sources for printers and other optical application devices, especially waveguide type second harmonics that convert semiconductor laser light with a wavelength of about 800 nm into blue light with a wavelength of about 400 nm. Generation element (SHG, Second Har
monic Generator).
【０００１】0001
【従来の技術】一般的に光学的非線形性を有する媒体内
に基本波光を入射することによりこれを第２高調波光そ
の他の高調波光に変換することができる。この際、上記
第２高調波への変換効率は媒体の光学的非線形性の強さ
や、媒体の拡がり等に関係する。すなわち変換効率を高
めることと共に、媒体内の各部で発生する第２高調波光
の位相を揃えて取り出すことが要求される。位相が不揃
いであると強い第２高調波光を得ることができない。2. Description of the Related Art Generally, fundamental wave light can be converted into second harmonic light or other harmonic light by making it incident on a medium having optical nonlinearity. At this time, the conversion efficiency to the second harmonic is related to the strength of the optical nonlinearity of the medium, the spread of the medium, and the like. That is, it is required to increase the conversion efficiency and to extract the second harmonic light generated in each part of the medium with the same phase. If the phases are uneven, strong second harmonic light cannot be obtained.
【０００２】上記の要件に適う方法として特開昭６１−
１８９６４号公報には図２に示すようにＬｉＮｂＯ３単
結晶基板１上にプロトン交換法（ＬｉＮｂＯ３のＬｉイ
オンの一部をプロトンに置換する方法）により光導波路
２を形成し、上記光導波路２の一端より基本波４１を入
射しチェレンコフ放射により発生した第２高調波４２を
取り出すことが開示されている。[0002] As a method that meets the above requirements, Japanese Patent Application Laid-Open No. 1986-
18964, as shown in FIG. 2, an optical waveguide 2 is formed on a LiNbO3 single crystal substrate 1 by a proton exchange method (a method of replacing some of the Li ions of LiNbO3 with protons), and one end of the optical waveguide 2 is It is disclosed that a fundamental wave 41 is inputted and a second harmonic 42 generated by Cerenkov radiation is extracted.
【０００３】また他の方法として１９８９年発行のＥｌ
ｅｌｃｔｒｏｎｉｃｓ，Ｌｅｔｔｅｒｓ誌、第２５巻、
第１１号、第７３１〜７３３頁には、図３に示すように
ＬｉＮｂＯ３単結晶基板１上に、基板１とは自発分極の
向きが逆向きの分極反転層３１を設け、さらに上記自発
分極の大きさが周期的に変化したり、または自発分極の
向きが周期的に反転するようにして光導波路２を設け、
基本波４１を入射して第２高調波間４２を得る方法が報
告されている。すなわち、基本波４１の一部は分極反転
層３１の光学的非線形性により第２高調波４２に変換さ
れる。[0003] As another method, El
electronics, Letters magazine, Volume 25,
No. 11, pages 731-733, as shown in FIG. The optical waveguide 2 is provided so that the size changes periodically or the direction of spontaneous polarization is periodically reversed,
A method has been reported in which a fundamental wave 41 is input and second harmonics 42 are obtained. That is, a part of the fundamental wave 41 is converted into a second harmonic wave 42 due to the optical nonlinearity of the polarization inversion layer 31.
【０００４】図３において分極反転層３１の厚みが一様
であると、光導波路２の各部で発生する第２高調波成分
の位相が不揃いとなり強い第２高調波出力が得られない
。そこで分極反転層３１の厚みを図示のように周期的に
変化させ、厚みの厚いところで発生する強い第２高調波
成分が同相で加算されるようにする。分極反転層３１の
ピッチはこのような第２高調波成分の同相加算を可能と
する値に設定される。上記分極反転層３１の生成方法に
ついては、例えば１９８９年発行のＩＥＥＥ、Ｐｈｏｔ
ｏｎｉｃｓ Ｔｅｃｈｎｏｌｏｇｙ Ｌｅｔｔｅｒｓ
誌、第１巻、第１０号、第３１６〜３１８頁にて、Ｌｉ
ＮｂＯ３単結晶基板１上にＳｉＯ２またはＴｉＯ２のパ
タ−ンを設けて熱処理する方法が報告されている。In FIG. 3, if the thickness of the polarization inversion layer 31 is uniform, the phases of the second harmonic components generated in each part of the optical waveguide 2 will be uneven, making it impossible to obtain a strong second harmonic output. Therefore, the thickness of the polarization inversion layer 31 is changed periodically as shown in the figure, so that the strong second harmonic components generated in the thick part are added in the same phase. The pitch of the polarization inversion layer 31 is set to a value that enables such in-phase addition of the second harmonic component. Regarding the method of producing the polarization inversion layer 31, for example, IEEE, Photo published in 1989,
onics Technology Letters
Magazine, Vol. 1, No. 10, pp. 316-318, Li
A method has been reported in which a pattern of SiO2 or TiO2 is provided on a NbO3 single crystal substrate 1 and then heat treated.
【０００５】図４は上記分極反転層３１の形成プロセス
を示す図である。まず、図４（ａ）に示すようにＬｉＮ
ｂＯ３基板１上にＴｉ膜による所定のパターン５１をホ
トリソグラフィにより設け、熱処理によりＴｉを図４（
ｂ）に示すように拡散させてＴｉ拡散層５２を形成する
。宮沢らは１９７９年のＪｏｕｒｎａｌ ｏｆ Ａｐｐ
ｌｉｅｄ Ｐｈｙｓｉｃｓ誌、第５０巻，第７号、４５
９９〜４６０３頁にて、上記Ｔｉ拡散層５２のキュリー
温度がＴｉ濃度ににもよるがＬｉＮｂＯ３基板１に較べ
て２０〜５０℃程度低下することを報告している。FIG. 4 is a diagram showing a process for forming the polarization inversion layer 31. First, as shown in FIG. 4(a), LiN
A predetermined pattern 51 made of a Ti film is provided on the bO3 substrate 1 by photolithography, and Ti is removed by heat treatment as shown in FIG.
A Ti diffusion layer 52 is formed by diffusion as shown in b). Miyazawa et al. 1979 Journal of App
Lied Physics Magazine, Volume 50, No. 7, 45
On pages 99-4603, it is reported that the Curie temperature of the Ti diffusion layer 52 is lowered by about 20-50°C compared to the LiNbO3 substrate 1, although it depends on the Ti concentration.
【０００６】ＬｉＮｂＯ３のような強誘電体の自発分極
Ｐｓは式（１）のように表すことができ、単結晶基板１
とＴｉ拡散層５２の自発分極Ｐｓの温度依存性は図６の
ようになる。これよりＴｉ拡散層５２の方がキュリー温
度Ｔｃ’、自発分極の大きさ共に基板１より小さいこと
がわかる。ただし、Ｃは定数である。[0006] Spontaneous polarization Ps of a ferroelectric material such as LiNbO3 can be expressed as shown in equation (1).
The temperature dependence of the spontaneous polarization Ps of the Ti diffusion layer 52 is as shown in FIG. From this, it can be seen that the Curie temperature Tc' and the magnitude of spontaneous polarization of the Ti diffused layer 52 are smaller than those of the substrate 1. However, C is a constant.
【数１】
これより、上記Ｔｉ拡散層５２のキュリー温度Ｔｃ’よ
り低い温度Ｔ０で加熱すると、自発分極の差により図４
（ｂ）に示すようにＴｉ拡散層５２と基板１の境界部に
負の電荷が誘起され、この電荷により図４（ｃ）に示す
ような矢印方向の電場Ｅが発生する。[Equation 1] From this, when heated at a temperature T0 lower than the Curie temperature Tc' of the Ti diffusion layer 52, the difference in spontaneous polarization causes
As shown in FIG. 4B, negative charges are induced at the boundary between the Ti diffusion layer 52 and the substrate 1, and this charge generates an electric field E in the direction of the arrow shown in FIG. 4C.
【０００７】上記電場Ｅの大きさが強誘電体固有の閾値
を超えると表面部の自発分極を反転させて分極反転層３
１が形成される。この分極反転層３１は温度を上記Ｔ０
から例えば常温に戻しても保存される。また、分極反転
層３１は電場Ｅの方向にその大きさに比例して伸びて形
成される。上記電場Ｅのｃ軸方向成分の大きさは式（２
）のようにあらわすことができるWhen the magnitude of the electric field E exceeds a threshold value specific to the ferroelectric material, the spontaneous polarization of the surface portion is reversed and the polarization inversion layer 3 is formed.
1 is formed. This polarization inversion layer 31 maintains the temperature above T0.
For example, it will be preserved even if it is returned to room temperature. Further, the polarization inversion layer 31 is formed to extend in the direction of the electric field E in proportion to its magnitude. The magnitude of the c-axis direction component of the electric field E is expressed by the formula (2
) can be expressed as
【数２】
ただし、ΔＰｓは図５に示したＬｉＮｂＯ３結晶とＴｉ
拡散層の自発分極差、εはＬｉＮｂＯ３のｃ軸方向の誘
電率、ｄはＴｉ拡散層５２の厚さ、ｌは基板１の厚さで
ある。また、θはＴｉ拡散５２と基板１の界面の接線と
ＬｉＮｂＯ３結晶のｃ軸とがなす角である。[Equation 2] However, ΔPs is the LiNbO3 crystal shown in Fig. 5 and the Ti
The spontaneous polarization difference of the diffusion layer, ε is the dielectric constant of LiNbO3 in the c-axis direction, d is the thickness of the Ti diffusion layer 52, and l is the thickness of the substrate 1. Further, θ is the angle between the tangent to the interface between the Ti diffusion 52 and the substrate 1 and the c-axis of the LiNbO3 crystal.
【０００８】上記図４に示した従来の方法では、Ｔｉの
内部拡散と分極反転が同時に進行する。とくに熱処理時
に基板表面と平行な方向の拡散（横拡散）が生じて拡散
層５２が横方向に伸びるので、拡散層５の周辺部の上記
ｃｏｓθの値が比較的大きくなり、これにより分極反転
層３１も同様な横方向に伸びた形となる。このため図４
（ｄ）に示すように、分極反転層同志が三角形状につな
がるようになる。１９９０年の応用物理学会秋季学術講
演会の予稿集２７−ａ−Ｐ−２には上記ＳｉＯ２または
ＴｉＯ２パタ−ンの代わりにＮｂを用いることが報告さ
れている。In the conventional method shown in FIG. 4, internal diffusion of Ti and polarization inversion proceed simultaneously. In particular, during heat treatment, diffusion in the direction parallel to the substrate surface (lateral diffusion) occurs and the diffusion layer 52 extends in the lateral direction, so the value of cos θ at the peripheral portion of the diffusion layer 5 becomes relatively large, and as a result, the polarization inversion layer 31 also has a similar horizontally extended shape. For this reason, Figure 4
As shown in (d), the polarization inversion layers become connected in a triangular shape. The use of Nb in place of the SiO2 or TiO2 pattern is reported in Proceedings of the 1990 Japan Society of Applied Physics Autumn Academic Conference 27-a-P-2.
【０００９】[0009]
【発明が解決しようとする課題】上記図２に示した方法
では、第２高調波出力４２のビ−ム形状が三日月型とな
るため波面収差が大きくなり、これを回折限界まで絞り
込むこと不可能に近いため、光ディスク装置には適用困
難という問題があった。また、図３や図４（ｄ）に示し
た分極反転層３１は上記出力光の絞り込み困難という問
題はないものの、その断面形状が三角波状であるため基
本波４１から第２高調波光４２への変換効率が低いこと
が問題であった。[Problem to be Solved by the Invention] In the method shown in FIG. 2, the beam shape of the second harmonic output 42 becomes crescent-shaped, resulting in large wavefront aberrations, and it is impossible to narrow this down to the diffraction limit. Since it is close to , there is a problem that it is difficult to apply it to optical disk devices. Further, although the polarization inversion layer 31 shown in FIGS. 3 and 4(d) does not have the problem of difficulty in narrowing down the output light, its cross-sectional shape is triangular wave-like, so the polarization inversion layer 31 shown in FIG. 3 and FIG. The problem was that the conversion efficiency was low.
【００１０】上記変換効率の改善に関して、Ｇ．Ａｒｖ
ｉｄｓｓｏｎｎらはＰｒｏｃｅｅｄｉｎｇｓ ｏｆ Ｉ
ｎｔｅｒｎａｔｉｏ−ｎａｌ Ｃｏｎｆｅｒｅｎｃｅ
ｏｎ Ｍａｔｅｒｉａｌｓ ｆｏｒ Ｎｏｎｌｉｎ−ｅ
ａｒ ａｎｄ Ｅｌｅｃｔｒｏ−ｏｐｔｉｃｓ誌，第１
〜６頁において、図４（ｄ）に示すような三角形状の分
極反転層３１を図６の３０のような矩形格子状にすれば
、第２高調波への変換効率は４倍以上に高まり、さらに
分極反転層の位置精度を緩和できることを理論的に明ら
かにした。しかしながら、現在のところ実際に得られる
分極反転部の断面形状は図３や図４（ｄ）に示すような
三角形状であり、理論が示唆するところの矩形形状が得
られないという問題があった。本発明の目的は上記断面
形状が矩形の分極反転格子３０の製造方法を提供し、さ
らにこの分極反転格子を用いた高効率で波面収差の小さ
い第二高調波発生素子を提供することにある。Regarding the improvement of the conversion efficiency, G. Arv
Proceedings of I
international-nal Conference
on Materials for Nonlin-e
ar and Electro-optics magazine, No. 1
-6 pages, if the triangular polarization inversion layer 31 as shown in FIG. 4(d) is made into a rectangular lattice shape as shown in 30 in FIG. 6, the conversion efficiency to the second harmonic will increase by more than four times. Furthermore, it was theoretically clarified that the positional accuracy of the polarization inversion layer can be relaxed. However, at present, the cross-sectional shape of the polarization inversion region actually obtained is triangular as shown in Fig. 3 and Fig. 4(d), and there is a problem that the rectangular shape suggested by theory cannot be obtained. . An object of the present invention is to provide a method for manufacturing the poled grating 30 having a rectangular cross-sectional shape, and further to provide a second harmonic generation element with high efficiency and small wavefront aberration using this poled grating.
【００１１】[0011]
【課題を解決するための手段】上記課題を解決するため
に、自発分極を有する非線形強誘電体単結晶基板上、ま
たは上記基板上に上記基板より屈折率が高くかつ自発分
極を有するように形成された薄膜結晶内に、キュリ−温
度を低下せしめる複数の不純物注入部を上記基板上の光
導波路と直行する向きにその断面形状が矩形状となるよ
うに設け、上記キュリ−温度より低い第１の温度で熱処
理して上記複数の不純物注入部の自発分極方向を上記基
板または上記薄膜結晶の自発分極方向に対して反転せし
めるようにする。[Means for Solving the Problems] In order to solve the above problems, a nonlinear ferroelectric single crystal substrate having spontaneous polarization, or formed on the above substrate so as to have a higher refractive index than the above substrate and have spontaneous polarization. A plurality of impurity implanted portions for lowering the Curie temperature are provided in the thin film crystal so as to have a rectangular cross section in a direction perpendicular to the optical waveguide on the substrate, and The spontaneous polarization direction of the plurality of impurity implanted parts is reversed with respect to the spontaneous polarization direction of the substrate or the thin film crystal by heat treatment at a temperature of .
【００１２】また、上記基板または上記薄膜結晶部にア
ルカリ金属イオンまたは遷移金属イオンを上記第１の温
度より低い３００℃以下の第２温度にて注入して上記不
純物注入部を形成するようにする。また、上記基板また
は上記薄膜結晶部に遷移金属イオンを３００℃以下の温
度で打ち込んで上記不純物注入部を形成するようにする
。また、上記基板または上記薄膜結晶部のイオンをアル
カリ金属イオンと交換して上記不純物注入部を形成する
ようにする。このため、上記基板または薄膜結晶上にイ
オン遮蔽マスクを設けて解離度１０￣４以下の弱酸と前
記弱酸のリチウム塩の混合物内で熱処理するようにする
。[0012] Further, the impurity implanted portion is formed by implanting alkali metal ions or transition metal ions into the substrate or the thin film crystal portion at a second temperature of 300° C. or less, which is lower than the first temperature. . Further, the impurity implanted portion is formed by implanting transition metal ions into the substrate or the thin film crystal portion at a temperature of 300° C. or lower. Further, the impurity implanted portion is formed by exchanging ions of the substrate or the thin film crystal portion with alkali metal ions. For this purpose, an ion shielding mask is provided on the substrate or thin film crystal, and the heat treatment is performed in a mixture of a weak acid having a degree of dissociation of 10° or less and a lithium salt of the weak acid.
【００１３】また、上記基板または上記薄膜結晶部をニ
オブ酸リチウム、またはタンタル酸リチウム、またはタ
ンタルニオブ酸リチウム材、または前記三種類にマグネ
シウムをドープしたものとする。また、上記第１の温度
による熱処理を温度範囲を９５０〜１１００℃にて水蒸
気を含む不活性ガスと酸素ガス中で行うようにする。The substrate or the thin film crystal portion may be made of lithium niobate, lithium tantalate, lithium tantalum niobate, or the above three materials doped with magnesium. Further, the heat treatment at the first temperature is performed in an inert gas containing water vapor and oxygen gas at a temperature range of 950 to 1100°C.
【００１４】[0014]
【作用】上記基板または上記薄膜結晶部にアルカリ金属
イオンまたは遷移金属イオンを上記第１の温度より低い
第２の温度にて注入すること、または遷移金属イオンを
３００℃以下の温度で打ち込むこと、または上記基板ま
たは上記薄膜結晶部のイオンをアルカリ金属イオンと交
換すること等の方法により、上記不純物注入部の断面形
状が矩形状に形成される。また、上記断面形状が矩形状
の不純物注入部をキュリ−温度より低い第１温度にて加
熱することにより、その自発分極が上記基板表面の法線
方向に成長するので、基板表面部に分極方向が基板また
は上記薄膜結晶とは反対方向の分極反転格子が形成され
る。[Operation] Injecting alkali metal ions or transition metal ions into the substrate or the thin film crystal portion at a second temperature lower than the first temperature, or implanting transition metal ions at a temperature of 300° C. or lower; Alternatively, the cross-sectional shape of the impurity implantation part is formed into a rectangular shape by a method such as exchanging ions of the substrate or the thin film crystal part with alkali metal ions. In addition, by heating the impurity implanted portion having a rectangular cross-sectional shape at a first temperature lower than the Curie temperature, its spontaneous polarization grows in the normal direction of the substrate surface, so that the polarization direction A polarization-inverted lattice is formed in which the polarization is opposite to that of the substrate or the thin film crystal.
【００１５】また、上記基板または上記薄膜結晶部をニ
オブ酸リチウム、またはタンタル酸リチウム、またはタ
ンタルニオブ酸リチウム材、または前記三種類にマグネ
シウムをドープしたものとすることにより、Ｔｉ等の遷
移金属イオンをその（０００１）方向にイオン打ち込み
して０．２μｍの深さにまで略一様で矩形波形状に注入
することができる。また、上記第１温度による熱処理を
９５０〜１１００℃にて水蒸気を含む不活性ガスと酸素
ガス中で行うことにより、基板内のＬｉイオンの外部拡
散が防止される。[0015] Furthermore, by making the substrate or the thin film crystal part made of lithium niobate, lithium tantalate, lithium tantalum niobate, or the above three materials doped with magnesium, transition metal ions such as Ti can be absorbed. Ions can be implanted in the (0001) direction to a depth of 0.2 μm substantially uniformly and in a rectangular wave shape. Further, by performing the heat treatment at the first temperature in an inert gas containing water vapor and oxygen gas at 950 to 1100° C., outward diffusion of Li ions in the substrate is prevented.
【００１６】[0016]
〔実施例 １〕図１（ａ）は本発明による第２高調波
発生素子実施例の原理的構造を示す斜視図、同図（ｂ）
は（ａ）図におけるＡ−Ｂ断面図である。ニオブ酸リチ
ウム（ＬｉＮｂＯ３）、またはタンタル酸リチウム（Ｌ
ｉＴａＯ３）、またはタンタルニオブ酸リチウム等より
なる基板１の表面部に、分極反転格子３２とプロトン交
換法により作製されたチャンネル型光導波路２が設けら
れている。以下、一例としてニオブ酸リチウム（ＬｉＮ
ｂＯ３）を用いた場合について説明を進める。ＬｉＮｂ
Ｏ３の＋ｃ面が基板１の表面に設定されるため、基板１
の自発分極の向きは表面の法線方向外向きである。これ
に対して分極反転格子３２の自発分極は基板１の自発分
極方向と反対向きになる。[Example 1] FIG. 1(a) is a perspective view showing the principle structure of an embodiment of the second harmonic generating element according to the present invention, and FIG. 1(b)
is a sectional view taken along line A-B in FIG. Lithium niobate (LiNbO3) or lithium tantalate (L
A polarization inversion grating 32 and a channel type optical waveguide 2 fabricated by a proton exchange method are provided on the surface of a substrate 1 made of iTaO3) or lithium tantalum niobate. Below, as an example, lithium niobate (LiN
The explanation will proceed regarding the case where bO3) is used. LiNb
Since the +c plane of O3 is set on the surface of substrate 1,
The direction of spontaneous polarization is outward in the normal direction of the surface. On the other hand, the spontaneous polarization of the polarization inversion grating 32 is opposite to the direction of spontaneous polarization of the substrate 1.
【００１７】光導波路２の左側より基本周波数の入射光
（基本波）４１が入射され、基板１の部分と分極反転格
子３２部分とを交互に通過する。分極反転格子３２の自
発分極の向きが基板１の自発分極方向に対して反転して
いるためその非線形光学係数の作用により、分極反転格
子３２内にて上記基本波光の一部は第２高調波光に変換
される。各分極反転格子３２内で発生した上記第２高調
波光成分は光導波路２内で加算されて出力第２高調波４
２として出射される。Incident light (fundamental wave) 41 having a fundamental frequency is input from the left side of the optical waveguide 2 and passes alternately through the substrate 1 portion and the polarization inversion grating 32 portion. Since the direction of spontaneous polarization of the polarization reversal grating 32 is reversed with respect to the spontaneous polarization direction of the substrate 1, a part of the fundamental wave light is converted into second harmonic light within the polarization reversal grating 32 due to the action of its nonlinear optical coefficient. is converted to The second harmonic optical components generated within each polarization inversion grating 32 are added within the optical waveguide 2 to output the second harmonic 4.
It is emitted as 2.
【００１８】図１において、分極反転格子３２の断面形
状を矩形に近い形としたことにより各分極反転格子３２
内における第２高調波への変換効率を高めることができ
、また、分極反転格子３間のピッチΛを式（３）により
得られる値に設定することにより各分極反転格子３内で
発生された第２高調波成分を同位相にして加算すること
ができる。In FIG. 1, each polarization inversion grating 32 has a nearly rectangular cross-sectional shape.
In addition, by setting the pitch Λ between the poled gratings 3 to the value obtained by equation (3), the The second harmonic components can be added in the same phase.
【数３】 ただしλは基本波の波長、Ｍは位相整合の次数である。[Math 3] Here, λ is the wavelength of the fundamental wave, and M is the order of phase matching.
【００１９】図７は本発明による上記分極反転格子３２
の生成過程図であり、図４に示した従来の分極反転層生
成プロセスと対比される。図７（ａ）は基板１上に室温
でＴｉ等の不純物の拡散層７１を矩形断面形状に設けた
状態を示している。図７（ｂ）は基板１をキュ−リ温度
以下のところで加熱している状態を示している。この熱
処理により、拡散層７１の横拡散が生じるのでその断面
形状は若干上拡がりの形となるものの、その側壁は基板
表面に対して略垂直であるため式２におけるθの値も略
９０度となり、ｃｏｓθの値は略ゼロとなる。したがっ
て側壁法線方向の電場Ｅはほとんどゼロであるためこの
方向には分局反転層が殆ど形成されない。FIG. 7 shows the polarization inversion grating 32 according to the present invention.
4 is a generation process diagram, and is compared with the conventional polarization inversion layer generation process shown in FIG. 4. FIG. 7A shows a state in which a diffusion layer 71 of an impurity such as Ti is provided on the substrate 1 at room temperature and has a rectangular cross section. FIG. 7(b) shows a state in which the substrate 1 is heated below the Curie temperature. This heat treatment causes lateral diffusion of the diffusion layer 71, so that its cross-sectional shape becomes slightly upwardly expanded, but since its sidewall is approximately perpendicular to the substrate surface, the value of θ in Equation 2 is also approximately 90 degrees. , cos θ are approximately zero. Therefore, since the electric field E in the direction normal to the sidewall is almost zero, almost no branching inversion layer is formed in this direction.
【００２０】これに対して拡散層７１底部は基板表面と
平行になるため、上記θの値は略０度で、すなわち、ｃ
ｏｓθの値は略１となり、底部法線方向の電場Ｅの値は
最大になる。したがって、図７（ｂ）に示すように基板
表面のｃ軸方向にのみ分極反転が成長する。これによる
分極反転格子３２は上記ｃ軸方向にのみに成長するので
、最終的には図７（ｃ）に示すように，当初の拡散層７
１と同様な矩形形状のアスペクト比の相互に孤立した分
極反転格子を形成することができる。図７（ｃ）におけ
る分極反転格子３２の形状は図６に示した理想的な分極
反転格子３０の形状に極めて近いので、これにより基本
波から第２高調波への変換効率を最大にできることがわ
かる。On the other hand, since the bottom of the diffusion layer 71 is parallel to the substrate surface, the value of θ is approximately 0 degrees, that is, c
The value of osθ is approximately 1, and the value of the electric field E in the direction normal to the bottom is maximum. Therefore, as shown in FIG. 7(b), polarization inversion grows only in the c-axis direction of the substrate surface. Since the resulting polarization inversion grating 32 grows only in the c-axis direction, it will eventually grow to the original diffusion layer 7 as shown in FIG. 7(c).
Mutually isolated poled gratings having a rectangular aspect ratio similar to that of 1 can be formed. Since the shape of the poled grating 32 in FIG. 7(c) is very close to the shape of the ideal poled grating 30 shown in FIG. 6, it is possible to maximize the conversion efficiency from the fundamental wave to the second harmonic. Recognize.
【００２１】次に図８−１、図８−２を用いて上記図７
に示した本発明による第２高調波発生素子の製造方法を
説明する。図８−１（ａ）は表面が＋ｃ面である１ｍｏ
ｌ％ＭｇＯド−プｚｃｕｔのＬｉＮｂＯ３基板１上にポ
ジ型のホトレジスト８１を設けた状態を示している。こ
のホトレジスト８１は厚み１μｍでスピンコート後、ホ
トリソグラフィによりパターニングされている。また、
パターンのラインとスペースの比は５／５〜９／１の範
囲が望ましく、ここでは熱処理時におけるイオンの横拡
散を考慮してこれを７／３とした。また、各分極反転格
子３内で発生した第２高調波成分の位相の調節して加算
できるようにするため、上記ホトレジスト８１としてパ
ターンピッチΛが２μｍから４μｍまで０．１μｍずつ
異なる２１種類を用意した。Next, using FIG. 8-1 and FIG. 8-2, the above-mentioned FIG.
A method of manufacturing the second harmonic generating element according to the present invention shown in FIG. Figure 8-1(a) shows 1mo whose surface is +c plane.
A positive photoresist 81 is shown on a 1% MgO-doped Zcut LiNbO3 substrate 1. This photoresist 81 has a thickness of 1 μm and is spin-coated and then patterned by photolithography. Also,
The line-to-space ratio of the pattern is preferably in the range of 5/5 to 9/1, and here, taking into consideration the lateral diffusion of ions during heat treatment, this was set to 7/3. In addition, in order to be able to adjust and add the phase of the second harmonic component generated in each polarization inversion grating 3, 21 types of photoresist 81 with pattern pitches Λ varying in 0.1 μm increments from 2 μm to 4 μm are prepared. did.
【００２２】マスク材料は一般的にイオンの種類により
異なるが、本発明のようにプロトン等のアルカリ金属を
打ち込んだり、Ｔｉ等の遷移金属を注入する場合におい
ても注入エネルギーを１０乃至５０ｋｅＶ程度にすれば
上記ホトレジスト８１をマスクとして用いることができ
る。上記イオンの種類はＬｉＮｂＯ３基板１のキュリー
温度を下げるものであれば何でもよく、図８−１（ｂ）
では室温でＴｉイオンを打ち込みＴｉ層７１を形成する
場合を示している。イオン打ち込み装置のイオン蒸発源
には四塩化チタン（ＴｉＣｌ４）を用い、注入エネルギ
ーを５０ｋｅＶ、注入量を１×１０１６ｉｏｎｓ／ｃｍ
とした。なお、上記注入イオンエネルギーは注入深さに
もよるが通常は１０から１５０ｋｅＶに設定する。また
、イオン打ち込み方向をＬｉＮｂＯ３結晶の（０００１
）方向とし、チャネリング現象によりＴｉイオンを０．
２μｍの深さまでほぼ一様の濃度で矩形状に注入できる
ようにした。The mask material generally varies depending on the type of ion, but even when implanting alkali metals such as protons or transition metals such as Ti as in the present invention, the implantation energy should be about 10 to 50 keV. For example, the photoresist 81 described above can be used as a mask. Any type of ion may be used as long as it lowers the Curie temperature of the LiNbO3 substrate 1, as shown in Figure 8-1(b).
In this example, a Ti layer 71 is formed by implanting Ti ions at room temperature. Titanium tetrachloride (TiCl4) was used as the ion evaporation source of the ion implantation device, the implantation energy was 50 keV, and the implantation amount was 1 x 1016 ions/cm.
And so. Note that the implantation ion energy is usually set at 10 to 150 keV, although it depends on the implantation depth. Also, the ion implantation direction was changed to (0001
) direction, and Ti ions are 0.
It was made possible to inject into a rectangular shape with a substantially uniform concentration up to a depth of 2 μm.
【００２３】次いでホトレジスト８１を除去し、図８−
１（ｃ）に示すように熱処理炉８３内で温度１０５０℃
にて６０分間熱処理する。この温度は基板のキュリ−温
度より低く、イオンの種類により異なるが通常は９５０
〜１１００℃であり、本実施例の場合は１０３０〜１１
００℃の範囲が望ましい。また８０℃のイオン交換水中
を通した酸素ガスを雰囲気ガスとして用い、上記熱処理
中におけるＬｉイオンの外部拡散を防止するようにした
。図８−１（ｄ）は上記熱処理後の基板の断面図である
。基板を切断研磨しフッ酸と硝酸の混合液中でエッチン
グしたところ、分極反転格子３２の断面形状は図示のよ
うにほぼ台形であることが確認できた。Next, the photoresist 81 is removed, and as shown in FIG.
As shown in 1(c), the temperature in the heat treatment furnace 83 is 1050°C.
Heat-treated for 60 minutes. This temperature is lower than the Curie temperature of the substrate, and varies depending on the type of ion, but is usually 950°C.
~1100°C, and in the case of this example it is 1030~11
A range of 00°C is desirable. In addition, oxygen gas passed through ion-exchanged water at 80° C. was used as an atmospheric gas to prevent external diffusion of Li ions during the heat treatment. FIG. 8-1(d) is a cross-sectional view of the substrate after the above heat treatment. When the substrate was cut, polished, and etched in a mixed solution of hydrofluoric acid and nitric acid, it was confirmed that the cross-sectional shape of the polarization inversion grating 32 was approximately trapezoidal as shown in the figure.
【００２４】次いでチャンネル型の光導波路２を形成す
る。まず、図８−２（ｅ）に示すように略１００ｎｍ厚
のＣｒ膜８４をスパッタリングにより成膜し、次いで図
８−２（ｆ）に示すように光導波路２用の幅２μｍの部
分をスピンコート厚１μｍのポジ型のホトレジストマス
クを用いてエッチングする。次いで図８−２（ｇ）に示
すように、解離度１０￣４以下の弱酸と弱酸のリチウム
塩の混合液内で熱処理する。例えば上記弱酸には安息香
酸を用い、弱酸のリチウム塩には１ｍｏｌ％の安息香酸
リチウムを用い、上記熱処理は２３０℃にて１０分間行
う。その後、取りだして冷却しＣｒ膜８４を除去する。
次いで基板１を４００℃の大気中にて４５分間加熱する
と幅３μｍ、深さ２μｍのチャンネル型光導波路２を得
ることができる。上記熱処理条件はプロトン交換の条件
によっても異なるが、３７５〜４００℃の温度範囲で３
０〜６０分加熱とすることが望ましい。Next, a channel type optical waveguide 2 is formed. First, as shown in FIG. 8-2(e), a Cr film 84 with a thickness of approximately 100 nm is formed by sputtering, and then, as shown in FIG. 8-2(f), a 2 μm-wide portion for the optical waveguide 2 is spun. Etching is performed using a positive photoresist mask with a coating thickness of 1 μm. Next, as shown in FIG. 8-2 (g), heat treatment is performed in a mixed solution of a weak acid with a degree of dissociation of 10° or less and a lithium salt of the weak acid. For example, benzoic acid is used as the weak acid, 1 mol% lithium benzoate is used as the lithium salt of the weak acid, and the heat treatment is performed at 230° C. for 10 minutes. Thereafter, it is taken out, cooled, and the Cr film 84 is removed. Next, by heating the substrate 1 in the atmosphere at 400° C. for 45 minutes, a channel type optical waveguide 2 having a width of 3 μm and a depth of 2 μm can be obtained. The above heat treatment conditions vary depending on the proton exchange conditions, but in the temperature range of 375 to 400℃
It is desirable to heat for 0 to 60 minutes.
【００２５】上記の工程により作製した第２高調波発生
素子の特性より基本波と第２高調波の屈折率Ｎ（ω）と
Ｎ（２ω）を求め、式（３）に従って分極反転格子３の
最適ピッチを割り出し、先に用意したピッチ間隔が０．
１μｍづつ異なる２１種類のホトレジストマスクの中か
らこの最適ピッチに最も近いものを選定し、之を用いて
最終的な第２高調波発生素子を作成する。このため、最
初の試作素子の光導波路２に、波長８３０ｎｍの垂直偏
光Ｔｉ−サファイアレーザ光をプリズムカップラを介し
て入射させたところ、基板の表面と垂直な方向に電場の
主成分を持つ一本のＴＭモードが励振され、その実効屈
折率Ｎ（ω）＝２．１７３０であった。また、上記、８
３０ｎｍの２分の１（４１５ｎｍ）にチューニングした
色素レーザ光により同様の測定を行った結果、二本のモ
ードが観測され、その低次モードの実効屈折率Ｎ（２ω
）は２．３０６６であった。また、カットバック法によ
り８３０ｎｍに対する光伝搬損失を測定したところThe refractive indexes N(ω) and N(2ω) of the fundamental wave and the second harmonic are determined from the characteristics of the second harmonic generating element manufactured by the above steps, and the refractive index of the polarization inversion grating 3 is determined according to equation (3). Determine the optimal pitch and set the pitch interval prepared earlier to 0.
Among 21 types of photoresist masks that differ by 1 μm, the one closest to this optimum pitch is selected and used to create the final second harmonic generating element. For this reason, when a vertically polarized Ti-sapphire laser beam with a wavelength of 830 nm was incident on the optical waveguide 2 of the first prototype device via a prism coupler, a single beam with the main component of the electric field in the direction perpendicular to the surface of the substrate was detected. The TM mode of was excited, and its effective refractive index N(ω)=2.1730. Also, above, 8
As a result of performing similar measurements using a dye laser beam tuned to half of 30 nm (415 nm), two modes were observed, and the effective refractive index of the lower mode was N(2ω
) was 2.3066. In addition, the optical propagation loss for 830 nm was measured using the cutback method.
【０
０２６】０．２８ｄＢ／ｃｍという良好な値を得た。式
（３）にＭ＝１として上記Ｎ（ω）＝２．１７３０とＮ
（２ω）＝２．３０６６を代入すると分極反転層のピッ
チは約３．１μｍとなる。したがって、Λ＝３．１μｍ
の試料をチャンネル長１０ｍｍに切りだして光の入射面
と出射面とを研磨し、その第二高調波発生効率を測定し
た。レーザ光源としてＴｉ−サファイアレーザを用い、
対物レンズによりチャンネル部端面に光を集光した。８
３０ｎｍの基本波光の４０ｍＷ入射に対する４１５ｎｍ
の第二高調波出力は２．５ｍＷであり、その変換効率は
フレネル反射損失分を除外すると８．５％であった。こ
の値は従来素子の変換効率に比べて一桁以上大きく、こ
のように改善された理由は分極反転格子３２の形状が従
来の三角形形状から矩形形状に近づいたためと考えられ
る。上記実験結果より、出力２００ｍＷの大出力半導体
レーザを結合効率５０％で光導波路へ結合した場合を想
定すると、略２１．３％の第２高調波変換効率が得られ
ることになり、これによる第２高調波出力２１．３ｍＷ
は光磁気型光ディスクや相変化型光ディスクの書き込み
、再生等を行うに十分な大きさである。0
[026] A good value of 0.28 dB/cm was obtained. In equation (3), M=1 and the above N(ω)=2.1730 and N
By substituting (2ω)=2.3066, the pitch of the polarization inversion layer becomes approximately 3.1 μm. Therefore, Λ=3.1μm
A sample was cut into a channel length of 10 mm, the light incident surface and the light exit surface were polished, and the second harmonic generation efficiency was measured. Using a Ti-sapphire laser as a laser light source,
Light was focused on the end face of the channel part using an objective lens. 8
415nm for 40mW incidence of 30nm fundamental wave light
The second harmonic output was 2.5 mW, and the conversion efficiency was 8.5% excluding Fresnel reflection loss. This value is more than an order of magnitude larger than the conversion efficiency of the conventional element, and the reason for this improvement is thought to be that the shape of the polarization inversion grating 32 approaches a rectangular shape from the conventional triangular shape. From the above experimental results, assuming that a high-power semiconductor laser with an output of 200 mW is coupled to an optical waveguide with a coupling efficiency of 50%, a second harmonic conversion efficiency of approximately 21.3% can be obtained, and this results in a second harmonic conversion efficiency of approximately 21.3%. 2nd harmonic output 21.3mW
is large enough to perform writing, reproduction, etc. on a magneto-optical optical disk or a phase change optical disk.
【００２７】〔実施例 ２〕図９は光導波部を基板の
表面からはみ出すように設けた本発明による第２高調波
発生素子の斜視図である。図９において、表面が＋ｃ面
である５ｍｏｌ％ＭｇＯドープのＺｃｕｔＬｉＮｂＯ３
単結晶基板９１上に通常自発分極が上向きの１ｍｏｌ％
ＭｇＯドープＬｉＮｂＯ３単結晶薄膜９２を設け、その
上に分極方向が下向きの分極反転格子９３を設けている
。
また、光導波部９４は基板の表面からリッジ型にはみ出
し、基本波光とその第二高調波を閉じ込めて伝搬する。
入射基本波光４と第２高調波出力５は共に基板表面に垂
直に偏光している。[Embodiment 2] FIG. 9 is a perspective view of a second harmonic generating element according to the present invention in which an optical waveguide is provided so as to protrude from the surface of a substrate. In FIG. 9, 5 mol% MgO-doped ZcutLiNbO3 whose surface is +c plane
1 mol% of normally upward spontaneous polarization on single crystal substrate 91
A MgO-doped LiNbO3 single crystal thin film 92 is provided, and a polarization inversion lattice 93 with a downward polarization direction is provided thereon. Further, the optical waveguide 94 protrudes from the surface of the substrate in a ridge shape, and confines and propagates the fundamental wave light and its second harmonic. Both the incident fundamental wave light 4 and the second harmonic output 5 are polarized perpendicularly to the substrate surface.
【００２８】図１０−１、図１０−２は上記図９の素子
の製造過程図である。まずＬｉＮｂＯ３単結晶薄膜９２
をＬｉＮｂＯ３単結晶基板９１上にエピタキシャル成長
させて生成する。上記単結晶薄膜９２の原料である１ｍ
ｏｌ％ＭｇＯドープのＬｉＮｂＯ３を２０ｍｏｌ％とフ
ラックス材料となる硼酸リチウムＬｉ２Ｂ２Ｏ４８０ｍ
ｏｌ％の混合体を作成するために、所定量の炭酸リチウ
ムＬｉ２ＣＯ３、硼酸Ｈ３ＢＯ３、五酸化ニオブＮｂ２
Ｏ５、酸化マグネシウムＭｇＯの各粉末を十分に混合し
てから白金るつぼに入れ、１２００℃の酸素および水蒸
気雰囲気下で３時間加熱して均一の溶融体とした。FIGS. 10-1 and 10-2 are process diagrams for manufacturing the element shown in FIG. 9. First, LiNbO3 single crystal thin film 92
is produced by epitaxial growth on a LiNbO3 single crystal substrate 91. 1 m which is the raw material for the single crystal thin film 92
20 mol% of ol%MgO-doped LiNbO3 and 480m of lithium borate Li2B2O as flux material
ol% mixture of lithium carbonate Li2CO3, boric acid H3BO3, niobium pentoxide Nb2
After thoroughly mixing O5 and magnesium oxide MgO powders, the mixture was placed in a platinum crucible and heated for 3 hours in an oxygen and water vapor atmosphere at 1200°C to form a uniform melt.
【００２９】次いで、＋ｃ面が光学研磨された５ｍｏｌ
％ＭｇＯドープのＺｃｕｔＬｉＮｂＯ３単結晶基板９１
を、６０℃／ｈの冷却速度で８００℃まで冷却した上記
溶融体中に浸漬し、その後、電気炉内で３０℃／ｈの冷
却速度で室温まで冷却して図１０−１（ａ）に示すよう
な１ｍｏｌ％ＭｇＯドープＬｉＮｂＯ３薄膜９２を２．
５μｍ成長させた基板９１を得た。なお、ＥＰＭＡによ
って上記薄膜９２内のＭｇ含有率を調べたところ略１ｍ
ｏｌ％であった。また、上記フラックス材料の添加量は
７０から９０ｍｏｌ％の範囲が望ましく、基板９１の上
記溶融体浸漬時間は薄膜９２の膜厚にもよるが、膜厚０
．５〜３μｍの範囲に対して１０〜３０分である。また
、フラックス材料としては上記硼酸リチウムの他にフッ
化リチウムＬｉＦ、フッ化カリウムＫＦ、五酸化バナジ
ウムＶ２Ｏ５等を用いることもできる。Next, 5 mol of the +c surface was optically polished.
%MgO doped ZcutLiNbO3 single crystal substrate 91
was immersed in the above melt that had been cooled to 800°C at a cooling rate of 60°C/h, and then cooled to room temperature at a cooling rate of 30°C/h in an electric furnace to form the material shown in Figure 10-1(a). A 1 mol% MgO-doped LiNbO3 thin film 92 as shown in 2.
A substrate 91 grown to a thickness of 5 μm was obtained. In addition, when the Mg content in the thin film 92 was examined by EPMA, it was approximately 1 m
It was ol%. Further, the amount of the flux material added is preferably in the range of 70 to 90 mol%, and the time for which the substrate 91 is immersed in the melt depends on the thickness of the thin film 92, but the film thickness is 0.
．． 10 to 30 minutes for a range of 5 to 3 μm. In addition to the above-mentioned lithium borate, lithium fluoride LiF, potassium fluoride KF, vanadium pentoxide V2O5, etc. can also be used as the flux material.
【００３０】上記薄膜９２を積層した基板９１はその後
、図１０−１（ｂ）に示すように水蒸気を含む酸素雰囲
気内でアニールして酸素の欠損を補うようにする。次い
で図１０−１（ｃ）に示すように、薄膜９２の上にホト
レジスト８１を１μｍ厚でスピンコートし、通常のホト
リソグラフィ技術により分極反転部の窓あけパターニン
グを行う。次いで図１０−１（ｄ）に示すように室温に
てＴｉイオンの打ち込みを行い、矩形形状のＴｉ注入部
８２を形成する。上記Ｔｉの代わりに、ＬｉＮｂＯ３基
板９１のキュリー温度を下げることのできるアルカリ金
属、遷移金属類を用いるようにしてもよい。上記パター
ンのライン・スペース比は次の熱処理におけるＴｉ注入
部８２の横拡散を考慮して７／３とした。このライン／
スペースの値は熱処理温度にもよるが５／５〜９／１の
範囲が好ましい。The substrate 91 on which the thin film 92 is laminated is then annealed in an oxygen atmosphere containing water vapor to compensate for oxygen deficiencies, as shown in FIG. 10-1(b). Next, as shown in FIG. 10-1(c), a photoresist 81 is spin-coated to a thickness of 1 μm on the thin film 92, and a window opening pattern of the polarization inversion portion is performed using a normal photolithography technique. Next, as shown in FIG. 10-1(d), Ti ions are implanted at room temperature to form a rectangular Ti implanted portion 82. Instead of Ti, an alkali metal or a transition metal that can lower the Curie temperature of the LiNbO3 substrate 91 may be used. The line-to-space ratio of the pattern was set to 7/3 in consideration of lateral diffusion of the Ti implanted portion 82 in the next heat treatment. This line/
Although the value of the space depends on the heat treatment temperature, it is preferably in the range of 5/5 to 9/1.
【００３１】また、Ｔｉイオン打ち込み装置のイオン蒸
発源には４塩化チタン（ＴｉＣｌ４）を用い、注入エネ
ルギーは５０ｋｅＶとした。この注入エネルギーは注入
深さにもよるが１０〜１５０ｋｅＶの範囲内である。ま
た、イオン打ち込みの方向をＬｉＮｂＯ３結晶基板９１
の（０００１）方向としてチャネリング現象によりＴｉ
イオンが０．２μｍの深さにまでほぼ一様に注入される
ようにする。Ｔｉ注入量は１×１０１６ｉｏｎｓ／ｃｍ
２である。次いで図１０−２（ｅ）に示すように、Ｌｉ
イオンの外部拡散を抑止するためにホトレジスト８１を
除去後に８０℃のイオン交換水中を通した酸素ガス雰囲
気中で１０５０℃にて６０分間熱処理し、分極反転格子
９３を生成する。上記熱処理温度は注入不純物にもよる
が、上記Ｔｉやアルカリ金属、遷移金属等のキュ−リ温
度Ｔｃが概略１１５０℃なのでこれより若干低めの９５
０〜１１００℃、とくに１０３０〜１１００℃の範囲が
好ましいことになる。Furthermore, titanium tetrachloride (TiCl4) was used as the ion evaporation source of the Ti ion implantation device, and the implantation energy was 50 keV. This implantation energy is in the range of 10 to 150 keV, depending on the implantation depth. Also, the direction of ion implantation is changed to the LiNbO3 crystal substrate 91.
Due to the channeling phenomenon, Ti
Ions are implanted almost uniformly to a depth of 0.2 μm. Ti implantation amount is 1×1016 ions/cm
It is 2. Next, as shown in FIG. 10-2(e), Li
In order to suppress external diffusion of ions, after removing the photoresist 81, heat treatment is performed at 1050° C. for 60 minutes in an oxygen gas atmosphere passed through 80° C. ion-exchanged water to produce a polarization-inverted lattice 93. The above heat treatment temperature depends on the implanted impurities, but since the Curie temperature Tc of the above Ti, alkali metals, transition metals, etc. is approximately 1150°C, it is slightly lower than 95°C.
A range of 0 to 1100°C, particularly 1030 to 1100°C is preferable.
【００３２】図１０−２（ｆ）は基板冷却後に光導波路
９４の方向に沿って基板を切断研磨し、フッ酸と硝酸の
混合液中によりエッチングして得られる分極反転部９３
の断面図である。分極反転部９３の断面形状はほぼ矩形
に形成されていることがわかる。次に図１０−２（ｇ）
に示すように、スピンコート厚１μｍのホトレジストマ
スク８１を用いて、薄膜９２の光導波路９４以外の部分
を２．０μｍほどエッチングしてからホトレジスト８１
を除去し、幅３μｍ、深さ２．０μｍのリッジタイプの
チャンネル型光導波路９４を形成した。FIG. 10-2(f) shows a polarization inversion part 93 obtained by cutting and polishing the substrate along the direction of the optical waveguide 94 after cooling the substrate, and etching it in a mixed solution of hydrofluoric acid and nitric acid.
FIG. It can be seen that the cross-sectional shape of the polarization inversion section 93 is approximately rectangular. Next, Figure 10-2 (g)
As shown in , using a photoresist mask 81 with a spin coating thickness of 1 μm, the portion of the thin film 92 other than the optical waveguide 94 is etched by about 2.0 μm, and then the photoresist 81 is etched.
was removed to form a ridge-type channel optical waveguide 94 having a width of 3 μm and a depth of 2.0 μm.
【００３３】上記の工程により作製した第２高調波発生
素子の特性より基本波と第２高調波の屈折率Ｎ（ω）と
Ｎ（２ω）を求め、式（３）に従って分極反転格子３の
最適ピッチを割り出し、先に用意したピッチ間隔が０．
１μｍづつ異なる２１種類のホトレジストマスクの中か
らこの最適ピッチに最も近いものを選定し、之を用いて
最終的な第２高調波発生素子を作成しその効率をチェッ
クする。このため、最初の試作素子の光導波路２に、波
長８３０ｎｍの垂直偏光Ｔｉ−サファイアレーザ光をプ
リズムカップラを介して入射させたところ、基板の表面
と垂直な方向に電場の主成分を持つ一本のＴＭモードが
励振され、その実効屈折率Ｎ（ω）＝２．１６８６であ
った。また、上記、８３０ｎｍの２分の１（４１５ｎｍ
）にチューニングした色素レーザ光により同様の測定を
行った結果、二本のモードが観測され、その低次モード
の実効屈折率Ｎ（２ω）は２．３０１６であった。また
、カットバック法により８３０ｎｍに対する光伝搬損失
を測定したところ１ｄＢ／ｃｍという良好な値を得た。The refractive indexes N(ω) and N(2ω) of the fundamental wave and the second harmonic are determined from the characteristics of the second harmonic generation element manufactured by the above steps, and the refractive indexes of the polarization inversion grating 3 are determined according to equation (3). Determine the optimal pitch and set the pitch interval prepared earlier to 0.
Among 21 types of photoresist masks that differ by 1 μm, the one closest to this optimum pitch is selected, used to create the final second harmonic generating element, and its efficiency is checked. For this reason, when a vertically polarized Ti-sapphire laser beam with a wavelength of 830 nm was incident on the optical waveguide 2 of the first prototype device via a prism coupler, a single beam with the main component of the electric field in the direction perpendicular to the surface of the substrate was detected. The TM mode of was excited, and its effective refractive index N(ω) was 2.1686. In addition, as mentioned above, one half of 830nm (415nm
), two modes were observed, and the effective refractive index N(2ω) of the lower mode was 2.3016. Further, when the optical propagation loss at 830 nm was measured by the cutback method, a good value of 1 dB/cm was obtained.
【００３４】式（３）にＭ＝１として上記Ｎ（ω）＝２
．１６８６とＮ（２ω）＝２．３０１６を代入すると分
極反転層のピッチΛは約３．１μｍとなる。したがって
、Λ＝３．１μｍの試料をチャンネル長１０ｍｍに切り
だして光の入射面と出射面とを研磨し、その第二高調波
発生効率を測定した。レーザ光源としてＴｉ−サファイ
アレーザを用い、対物レンズによりチャンネル部端面に
光を集光した。８３０ｎｍの基本波光の４０ｍＷ入射に
対する４１５ｎｍの第二高調波出力の大きさは２ｍＷで
あり、その変換効率はフレネル反射損失ぶんを除外する
と６．８％となる。上記変換効率は一般的に入力強度に
比例して向上するので、例えば出力２００ｍＷの大出力
半導体レーザを結合効率５０％で光導波路へ結合した場
合を想定すると、略１７％の第２高調波変換効率が得ら
れることになり、光磁気型光ディスクや相変化型光ディ
スクの書き込み、再生に十分な大きさの第二高調波出力
１７ｍＷが得られることになる。[0034] In equation (3), M=1 and the above N(ω)=2
．． By substituting 1686 and N(2ω)=2.3016, the pitch Λ of the polarization inversion layer becomes approximately 3.1 μm. Therefore, a sample with Λ=3.1 μm was cut into a channel length of 10 mm, the light incident surface and the light exit surface were polished, and the second harmonic generation efficiency was measured. A Ti-sapphire laser was used as a laser light source, and light was focused on the end face of the channel portion using an objective lens. The magnitude of the second harmonic output at 415 nm with respect to the 40 mW incidence of the fundamental wave light at 830 nm is 2 mW, and the conversion efficiency is 6.8% when Fresnel reflection loss is excluded. The above conversion efficiency generally increases in proportion to the input intensity, so for example, assuming that a high-power semiconductor laser with an output of 200 mW is coupled to an optical waveguide with a coupling efficiency of 50%, the second harmonic conversion will be approximately 17%. Efficiency can be obtained, and a second harmonic output of 17 mW, which is sufficient for writing and reproducing on magneto-optical optical discs and phase change optical discs, can be obtained.
【００３５】〔実施例 ３〕図１および図９に示した
本発明の第二高調波発生素子は図１１−１、図１１−２
に示すようなイオン交換法によっても製造することがで
きる。以下一例として図１の第二高調波発生素子を製造
する場合につき説明する。まず、図１１−１（ａ）に示
すように、ＭｇＯが５ｍｏｌ％ドープされたＬｉＮｂＯ
３の基板１上にスパッタリング法によりＣｒ膜８４を厚
み約１００ｎｍに成膜する。次にＣｒ膜８４をホトリソ
グラフィにより図１１−１（ｂ）に示すようにパターニ
ングする。このため約１μｍ厚にスピンコートしたホト
レジストをパタ−ニングして、パターンピッチ２〜４μ
ｍ、ライン／スペース８／２０のパタ−ンを形成しこれ
をマスクトしてとしてＣｒパターンをエッチングする。
なお、上記パターンにはピッチが０．１μｍずつ異なる
ものを２１種類用意した。[Example 3] The second harmonic generation element of the present invention shown in FIGS. 1 and 9 is shown in FIGS. 11-1 and 11-2.
It can also be produced by an ion exchange method as shown in . As an example, the case of manufacturing the second harmonic generating element shown in FIG. 1 will be described below. First, as shown in FIG. 11-1(a), LiNbO doped with 5 mol% MgO
A Cr film 84 having a thickness of about 100 nm is formed on the substrate 1 of No. 3 by sputtering. Next, the Cr film 84 is patterned by photolithography as shown in FIG. 11-1(b). For this purpose, a photoresist spin-coated to a thickness of about 1 μm is patterned, and the pattern pitch is 2 to 4 μm.
A pattern of 8/20 lines/spaces is formed, and a Cr pattern is etched using this as a mask. Note that 21 types of the above patterns were prepared, each having a pitch different by 0.1 μm.
【００３６】次に図１１−１（ｃ）に示すように、１ｍ
ｏｌ％の安息香酸リチウムを添加した安息香酸を石英容
器中８５にいれ、加熱、溶融し、その溶融液８６中に基
板を浸漬する。溶融液８６の温度は１６０℃、浸漬時間
は１０分である。これにより、図１１−１（ｄ）に示す
ように、プロトン交換層１１１が深さ約０．１μｍに形
成される。ついでＣｒ膜を除去して図１１−２（ｅ）に
示すように、熱処理炉８３の中で温度１０３５℃にて６
０分間熱処理を行うと図１１−２（ｆ）に示すような矩
形に近い深さ約３μｍの分極反転層３を形成することが
できる。この熱処理温度は９５０℃から１１００℃の範
囲が望ましく、また雰囲気には８０℃のイオン交換水中
を通した酸素ガスを用いてＬｉ２Ｏの外部拡散を防止す
る。Next, as shown in FIG. 11-1(c), 1 m
Benzoic acid to which 1 ol % of lithium benzoate has been added is placed in a quartz container 85, heated and melted, and the substrate is immersed in the melt 86. The temperature of the melt 86 is 160° C., and the immersion time is 10 minutes. Thereby, as shown in FIG. 11-1(d), a proton exchange layer 111 is formed to a depth of about 0.1 μm. Then, the Cr film is removed and treated in a heat treatment furnace 83 at a temperature of 1035°C for 6 hours as shown in FIG.
When the heat treatment is performed for 0 minutes, a polarization inversion layer 3 having a nearly rectangular shape and a depth of about 3 μm as shown in FIG. 11-2(f) can be formed. The heat treatment temperature is preferably in the range of 950° C. to 1100° C., and oxygen gas passed through 80° C. ion-exchanged water is used as the atmosphere to prevent external diffusion of Li2O.
【００３７】最後に上記実施例１と同様にしてプロトン
交換光導波路２を形成する。このようにして作製した第
２高調波発生素子の効率は実施例１にて作成した同素子
とほぼ同等である。なお上記図１１の製造方法により図
９に示した第二高調波発生素子を作成する場合には、薄
膜結晶９２を形成した後に分極反転格子を作製するよう
にする。Finally, the proton exchange optical waveguide 2 is formed in the same manner as in Example 1 above. The efficiency of the second harmonic generation element thus manufactured is almost the same as that of the element manufactured in Example 1. Note that when the second harmonic generation element shown in FIG. 9 is manufactured by the manufacturing method shown in FIG. 11, the polarization inversion grating is manufactured after forming the thin film crystal 92.
【００３８】[0038]
【発明の効果】本発明においては、ニオブ酸リチウム、
またはタンタル酸リチウム、またはタンタルニオブ酸リ
チウム材、または前記三種類にマグネシウムをドープし
た基板または薄膜結晶部に、断面形状が矩形の不純物注
入部を形成することができるので、これをキュリ−温度
より低い温度にて加熱することにより自発分極方向が上
記基板表面の法線方向であり、かつ基板の分極方向とは
反対の分極反転格子を矩形断面形状に形成することがで
き、これにより従来の第２高調波変換素子に較べて変換
効率を一桁以上改善することができる。例えば、波長８
３０ｎｍ、出力２００ｍＷの大出力半導体レーザを結合
効率５０％で光導波路へ結合するような場合には波長４
１５ｎｍの第２高調波出力を変換効率１７〜２１％で得
ることができ、これにより光磁気型光ディスクや相変化
型光ディスクの書き込み／再生を短波長化して、記録密
度を大きく向上することができる。[Effect of the invention] In the present invention, lithium niobate,
Alternatively, it is possible to form an impurity implantation part with a rectangular cross section in a substrate or thin film crystal part doped with lithium tantalate, lithium tantalum niobate material, or the above three types of magnesium. By heating at a low temperature, a polarization inversion lattice whose spontaneous polarization direction is normal to the substrate surface and opposite to the polarization direction of the substrate can be formed with a rectangular cross-sectional shape. Conversion efficiency can be improved by one order of magnitude or more compared to a two-harmonic conversion element. For example, wavelength 8
When coupling a high-power semiconductor laser with a wavelength of 30 nm and an output of 200 mW to an optical waveguide with a coupling efficiency of 50%, the wavelength is 4.
A second harmonic output of 15 nm can be obtained with a conversion efficiency of 17 to 21%, making it possible to shorten the wavelength for writing/reproducing on magneto-optical optical disks and phase change optical disks, greatly improving recording density. .
【図１】本発明により作製した第二高調波発生素子の概
念図ある。FIG. 1 is a conceptual diagram of a second harmonic generation element manufactured according to the present invention.
【図２】チェレンコフ放射を用いた従来の第二高調波発
生素子の側面図である。FIG. 2 is a side view of a conventional second harmonic generation element using Cerenkov radiation.
【図３】分極反転層を用いた従来の第二高調波発生素子
の側面図である。FIG. 3 is a side view of a conventional second harmonic generation element using a polarization inversion layer.
【図４】従来の製造方法における分極反転格子の形成過
程図である。FIG. 4 is a process diagram of forming a polarization inversion grating in a conventional manufacturing method.
【図５】強誘電体結晶における自発分極の温度特性図で
ある。FIG. 5 is a temperature characteristic diagram of spontaneous polarization in a ferroelectric crystal.
【図６】理想的な分極反転格子の形状を示す側面図であ
る。FIG. 6 is a side view showing the shape of an ideal poled grating.
【図７】本発明の製造方法における分極反転格子の形成
過程図である。FIG. 7 is a process diagram of forming a polarization inversion grating in the manufacturing method of the present invention.
【図８−１】本発明による第二高調波発生素子の製造工
程図である。FIG. 8-1 is a manufacturing process diagram of a second harmonic generation element according to the present invention.
【図８−２】本発明による第二高調波発生素子の製造工
程図である。FIG. 8-2 is a manufacturing process diagram of a second harmonic generation element according to the present invention.
【図９】本発明によるリッジ型光導波路を有する第２高
調波発生素子の概略図である。FIG. 9 is a schematic diagram of a second harmonic generation element having a ridge-type optical waveguide according to the present invention.
【図１０−１】図９の素子の製造工程図である。10-1 is a manufacturing process diagram of the element shown in FIG. 9; FIG.
【図１０−２】図９の素子の製造工程図である。10-2 is a manufacturing process diagram of the element shown in FIG. 9; FIG.
【図１１−１】本発明による他の分極反転格子の生成過
程図である。FIG. 11-1 is a diagram showing the process of generating another polarization inversion grating according to the present invention.
【図１１−２】本発明による他の分極反転格子の生成過
程図である。FIG. 11-2 is a diagram showing the production process of another polarization inversion grating according to the present invention.
１ 基板 ２ 光導波路 ４１ 基本波 ４２ 第２高調波 ３０ 分極反転格子 ３１ 分極反転層 ３２ 分極反転格子 ５１ Ｔｉパタ−ン ５２ Ｔｉ拡散層 ７１ Ｔｉ拡散層 ８１ ホトレジスト ８３ 熱処理炉 ８４ Ｃｒ膜 ９１ 基板 ９２ 単結晶薄膜 ９４ 光導波路 1 Board 2 Optical waveguide 41 Fundamental wave 42 Second harmonic 30 Polarization inversion lattice 31 Polarization inversion layer 32 Polarization inversion lattice 51 Ti pattern 52 Ti diffusion layer 71 Ti diffusion layer 81 Photoresist 83 Heat treatment furnace 84 Cr film 91 Board 92 Single crystal thin film 94 Optical waveguide
Claims (8)
晶基板上に上記基板のキュリ−温度を低下せしめる複数
の不純物注入部を上記基板上の光導波路と直行する向き
に設け、次いで上記キュリ−温度より低い第１の温度に
て熱処理して上記複数の不純物注入部の自発分極方向を
上記基板の自発分極方向に対して反転せしめるようにし
たレ−ザ光の第２高調波発生素子の製造方法において、
上記基板表面の不純物注入部の断面形状を矩形状とする
ようにしたことを特徴とする誘電体分極反転格子を備え
たレ−ザ光の第２高調波発生素子製造方法。1. A nonlinear ferroelectric single crystal substrate having spontaneous polarization is provided with a plurality of impurity implanted portions for lowering the Curie temperature of the substrate in a direction perpendicular to the optical waveguide on the substrate, and then the Curie temperature is Manufacturing a second harmonic generation element for laser light, which is heat-treated at a first temperature lower than that temperature to reverse the spontaneous polarization direction of the plurality of impurity implanted parts with respect to the spontaneous polarization direction of the substrate. In the method,
A method for manufacturing a second harmonic generation element for laser light equipped with a dielectric polarization inversion grating, characterized in that the cross-sectional shape of the impurity implanted portion on the surface of the substrate is rectangular.
ンまたは遷移金属イオンを第２の温度にて上記基板に注
入して上記不純物注入部を形成し、上記第１の温度にて
加熱処理して上記不純物注入部の上記自発分極方向を上
記基板の自発分極方向に対して反転するようにし、第２
の温度を第１の温度より低く設定するようにしたことを
特徴とする誘電体分極反転格子を備えたレ−ザ光の第２
高調波発生素子製造方法。2. In claim 1, the impurity implanted portion is formed by implanting alkali metal ions or transition metal ions into the substrate at a second temperature, and the impurity implantation portion is formed by heat treatment at the first temperature. The spontaneous polarization direction of the impurity implanted portion is reversed with respect to the spontaneous polarization direction of the substrate, and the second
A second laser beam equipped with a dielectric poled grating characterized in that the temperature of the second laser beam is set lower than the first temperature.
A method for manufacturing a harmonic generation element.
とアルカリ金属イオンとイオン交換して上記不純物注入
部を形成するようにしたことを特徴とする誘電体分極反
転格子を備えたレ−ザ光の第２高調波発生素子製造方法
。3. A laser beam having a dielectric poled grating according to claim 2, wherein the impurity implantation portion is formed by ion exchange between ions of the substrate and alkali metal ions. A method for manufacturing a second harmonic generating element.
率が高くかつ自発分極を有するように上記基板上に形成
された薄膜結晶内に、上記基板のキュリ−温度を低下せ
しめる複数の不純物注入部を上記基板上の光導波路と直
行する向きに設け、次いで上記キュリ−温度より低い温
度にて熱処理して上記複数の不純物注入部の自発分極方
向を上記基板の自発分極方向に対して反転せしめるよう
にしたことを特徴とする誘電体分極反転格子を備えたレ
−ザ光の第２高調波発生素子製造方法。4. According to claim 1, a plurality of impurity implanted portions for lowering the Curie temperature of the substrate are formed in a thin film crystal formed on the substrate so as to have a higher refractive index than the substrate and have spontaneous polarization. is provided in a direction perpendicular to the optical waveguide on the substrate, and then heat treated at a temperature lower than the Curie temperature to reverse the spontaneous polarization direction of the plurality of impurity implanted parts with respect to the spontaneous polarization direction of the substrate. 1. A method for manufacturing a second harmonic generation element for laser light equipped with a dielectric polarization inversion grating, characterized in that:
、上記基板をニオブ酸リチウム（化学式ＬｉＮｂＯ３）
、またはタンタル酸リチウム（化学式ＬｉＴａＯ３）、
またはタンタルニオブ酸リチウム 【化１】 、または前記三種類の基板内にマグネシウムをドープし
たものとすることを特徴とする誘電体分極反転格子を備
えたレ−ザ光の第２高調波発生素子の製造方法。5. In any one of claims 1 to 3, the substrate is made of lithium niobate (chemical formula: LiNbO3).
, or lithium tantalate (chemical formula LiTaO3),
or lithium tantalum niobate [Chemical formula 1], or a second harmonic generation element for laser light equipped with a dielectric polarization inversion grating, characterized in that magnesium is doped in the above three types of substrates. Production method.
された薄膜結晶を上記オブ酸リチウム、上記またはタン
タル酸リチウム、または上記タンタルニオブ酸リチウム
、または前記三種類の基板内にマグネシウムをドープし
たものとすることを特徴とする誘電体分極反転格子を備
えたレ−ザ光の第２高調波発生素子製造方法。6. In claim 4, the thin film crystal formed on the substrate is made of the lithium oxate, the lithium tantalate, the lithium tantalum niobate, or the three types of substrates doped with magnesium. 1. A method for manufacturing a second harmonic generation element for laser light equipped with a dielectric polarization inversion grating.
、上記第１の温度を９５０℃ないし１１００℃の範囲と
し、上記第１の温度による熱処理を水蒸気を含む不活性
ガスおよび酸素ガス中で行うようにしたことを特徴とす
る誘電体分極反転格子を備えたレ−ザ光の第２高調波発
生素子製造方法。7. In any one of claims 1 to 6, the first temperature is in a range of 950° C. to 1100° C., and the heat treatment at the first temperature is performed in an inert gas containing water vapor and oxygen gas. A method for manufacturing a second harmonic generation element for laser light equipped with a dielectric polarization inversion grating, characterized in that
、上記基板または薄膜結晶上にイオン遮蔽マスクを設け
て解離度１０￣４以下の弱酸と弱酸のリチウム塩の混合
物内で熱処理するようにしたことを特徴とする誘電体分
極反転格子を備えたレ−ザ光の第２高調波発生素子製造
方法。8. According to any one of claims 1 to 6, an ion shielding mask is provided on the substrate or thin film crystal, and the heat treatment is performed in a mixture of a weak acid and a lithium salt of the weak acid with a degree of dissociation of 10￣ or less. A method for manufacturing a second harmonic generation element for laser light equipped with a dielectric polarization inversion grating, characterized in that:
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10606091A JPH04335329A (en) | 1991-05-10 | 1991-05-10 | Production of second harmonic generating element having dielectric polarization inversion grating |
| US07/879,361 US5274727A (en) | 1991-05-10 | 1992-05-07 | Second harmonic generator and method of fabrication thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10606091A JPH04335329A (en) | 1991-05-10 | 1991-05-10 | Production of second harmonic generating element having dielectric polarization inversion grating |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH04335329A true JPH04335329A (en) | 1992-11-24 |
Family
ID=14424072
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10606091A Pending JPH04335329A (en) | 1991-05-10 | 1991-05-10 | Production of second harmonic generating element having dielectric polarization inversion grating |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH04335329A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5412502A (en) * | 1992-01-24 | 1995-05-02 | Hitachi Metals, Ltd. | Second harmonic generating element and the production method thereof |
| WO2006082930A1 (en) * | 2005-02-07 | 2006-08-10 | Hochiki Corporation | Heat detector and method for manufacturing heat detecting element |
| JP2006215000A (en) * | 2005-02-07 | 2006-08-17 | Hochiki Corp | Method for manufacturing thermal sensing element |
| US8463082B2 (en) | 2010-09-13 | 2013-06-11 | Ricoh Company, Ltd. | Manufacturing method for electrooptic element and optical deflector including electrooptic element |
-
1991
- 1991-05-10 JP JP10606091A patent/JPH04335329A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5412502A (en) * | 1992-01-24 | 1995-05-02 | Hitachi Metals, Ltd. | Second harmonic generating element and the production method thereof |
| WO2006082930A1 (en) * | 2005-02-07 | 2006-08-10 | Hochiki Corporation | Heat detector and method for manufacturing heat detecting element |
| JP2006215000A (en) * | 2005-02-07 | 2006-08-17 | Hochiki Corp | Method for manufacturing thermal sensing element |
| GB2438985A (en) * | 2005-02-07 | 2007-12-12 | Hochiki Co | Heat detector and method for manufacturing heat detecting element |
| GB2438985B (en) * | 2005-02-07 | 2009-04-08 | Hochiki Co | Heat detector and method for manufacturing heat detecting element |
| US7896544B2 (en) | 2005-02-07 | 2011-03-01 | Hochiki Corporation | Heat detector and method of manufacturing heat detecting element |
| US8463082B2 (en) | 2010-09-13 | 2013-06-11 | Ricoh Company, Ltd. | Manufacturing method for electrooptic element and optical deflector including electrooptic element |
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